The electrical generators currently available in the market mainly include diesel electrical generators, solar power electrical generators, and wind power electrical generators. The wind power electrical generators mainly rely on wind power to rotate the wind turbines so as to generate electrical power. However, once the wind speed is too high, the rotating speed of the wind turbine will increase by a large amount so that the operation of the wind turbine becomes unstable, which may damage the blades, the electrical generator, the control system and etc. As a result, the wind power electrical generator will not be ale to function, and the range of wind speed that is compatible with the wind power electrical generator is limited. To solve the above problem, some wind power electrical generators control the rotation speed of the wind turbine by hydraulic pressure and electronically controlled speed adjustment mechanisms. However, the structures of the wind power electrical generators are relatively complicated and the manufacturing thereof is relatively difficult.